Got this to test Voltage/current output on the various chargers lying in the house. I had a feeling with the Xiaomi Charger, that it's not putting out correct voltage or current. Testing to be done over the weekend. Pretty straightforward. You plug the male USB into the output of whatever you want to measure from, and the cable/load plugs into the female port above. Here's a No load 0 Amp reading. The display alternates between Current and Voltage every 5 seconds. The Voltage reading of a good USB charger should be higher than 5V, since it tends to drop under load. The iPhone 6S under charging. Surprised to see it pull 1.98, nearly 2 Amps! More testing to come.